保存以 0 开头的数字时保留前导零

Question

I am trying to save a list of site codes, for example:

site_codes = [1302,9033,1103,5005,0016]

Then I want to add the site code to URLs before running web scraping, using site_codes[i] , for example:

for i in range(len(site_codes)): 
  
  Data_site_A.append("https://.../"+str(parameters[i])+"site="+str(site_codes[0]))
  Data_site_B.append("https://.../"+str(parameters[i])+"site="+str(site_codes[1]))

But I can not save 0016 into the list just like other numbers. I have tried many ways including:

# make a string
str("{0}{1}{2}".format(0,0,16))

# fill the 0
"%04d" % 16

But they all return '0016' instead of 0016 . So when I input '0016' into the urls, it won't work, because it is not a number.

Is there a way to save this number just as 0016 ? Or since that print("%04d" % 16) will print out a pure 0016 , is there a way to save the output from there?

For the desired output, the computer should interpret it as:

"https://...."+str(parameters[i])+"site=0016")

Answer 1

# use regular expression

import re

site_codes = '''
         site code:
         site_A: 1302
         site_B: 9033
         site_C: 1103
         site_D: 5005
         site_E: 0016
         '''

site_codes = re.findall(r'\d+',site_codes)

for i in range(len(site_codes)): 
    Data_site_A.append("https://.../"+str(parameters[i])+"site="+str(site_codes[0]))
    Data_site_B.append("https://.../"+str(parameters[i])+"site="+str(site_codes[1]))

Answer 2

Use str.zfill() to add leading zeros to a number;
Call str(object) with a number as object to convert it to a string.
Call str.zfill(width) on the numeric string to pad it with 0 to the specified width.

print(a_number)

OUTPUT=
123

Convert a_number to a string

number_str = str(a_number)

Pad number_str with zeros to 5 digits

zero_filled_number = number_str.zfill(5)

print(zero_filled_number)

OUTPUT=
00123

Answer 3

Assuming that you really do have a list of integers that can't be retained as strings and want to create the URLs. Also assuming that you are using Python 3.6 or above, you can achieve this with a simple f-string .

print(f"https://.../{str(parameters[i])}site={site_codes[1]:04d}")

This will pad with leading zeros without the need to resort to zfill.

Alternatively, or if you're running Python below 3.6, this will also work:

print("https://.../{}site={:04d}".format(str(parameters[i]), site_codes[1]))

With a site code of 16, both of the above will give you

https://.../parametersite=0016